Stabilize default_alloc_error_handler
Tracking issue: #66741
This turns `feature(default_alloc_error_handler)` on by default, which causes the compiler to automatically generate a default OOM handler which panics if `#[alloc_error_handler]` is not provided.
The FCP completed over 2 years ago but the stabilization was blocked due to an issue with unwinding. This was fixed by #88098 so stabilization can be unblocked.
Closes#66741
Track where diagnostics were created.
This implements the `-Ztrack-diagnostics` flag, which uses `#[track_caller]` to track where diagnostics are created. It is meant as a debugging tool much like `-Ztreat-err-as-bug`.
For example, the following code...
```rust
struct A;
struct B;
fn main(){
let _: A = B;
}
```
...now emits the following error message:
```
error[E0308]: mismatched types
--> src\main.rs:5:16
|
5 | let _: A = B;
| - ^ expected struct `A`, found struct `B`
| |
| expected due to this
-Ztrack-diagnostics: created at compiler\rustc_infer\src\infer\error_reporting\mod.rs:2275:31
```
The new implementation doesn't use weak lang items and instead changes
`#[alloc_error_handler]` to an attribute macro just like
`#[global_allocator]`.
The attribute will generate the `__rg_oom` function which is called by
the compiler-generated `__rust_alloc_error_handler`. If no `__rg_oom`
function is defined in any crate then the compiler shim will call
`__rdl_oom` in the alloc crate which will simply panic.
This also fixes link errors with `-C link-dead-code` with
`default_alloc_error_handler`: `__rg_oom` was previously defined in the
alloc crate and would attempt to reference the `oom` lang item, even if
it didn't exist. This worked as long as `__rg_oom` was excluded from
linking since it was not called.
This is a prerequisite for the stabilization of
`default_alloc_error_handler` (#102318).
If we fail to locate a native library that we are linking with, it could
be the case the user entered a complete file name like `foo.lib` or
`libfoo.a` when we expect them to simply provide `foo`.
In this situation, we now detect that case and suggest the user only
provide the library name itself.
FIX - ambiguous Diagnostic link in docs
UPDATE - rename diagnostic_items to IntoDiagnostic and AddToDiagnostic
[Gardening] FIX - formatting via `x fmt`
FIX - rebase conflicts. NOTE: Confirm wheather or not we want to handle TargetDataLayoutErrorsWrapper this way
DELETE - unneeded allow attributes in Handler method
FIX - broken test
FIX - Rebase conflict
UPDATE - rename residual _SessionDiagnostic and fix LintDiag link
Suggested by the team in this Zulip Topic https://rust-lang.zulipchat.com/#narrow/stream/336883-i18n/topic/.23100717.20SessionDiagnostic.20on.20Handler
Handler already has almost all the capabilities of ParseSess when it comes to diagnostic emission, in this migration we only needed to add the ability to access source_map from the emitter in order to get a Snippet and the start_point. Not sure if this is the best way to address this gap
- ... when creating diagnostics in rustc_metadata
- use the error_code! macro
- pass macro output to diag.code()
- use fluent from within manual implementation of SessionDiagnostic
- emit the untested errors in case they occur in the wild
- stop panicking in the probably-not-dead code, add fixme to write test
